Netty源码分析-MultithreadEventExecutorGroup

 

MultithreadEventExecutorGroup

public abstract class MultithreadEventExecutorGroup extends AbstractEventExecutorGroup {

    private final EventExecutor[] children;
    private final Set readonlyChildren;
    private final AtomicInteger terminatedChildren = new AtomicInteger();
    private final Promise terminationFuture = new DefaultPromise(GlobalEventExecutor.INSTANCE);
    private final EventExecutorChooserFactory.EventExecutorChooser chooser;

    /**
     * Create a new instance.
     *
     * @param nThreads          the number of threads that will be used by this instance.
     * @param threadFactory     the ThreadFactory to use, or {@code null} if the default should be used.
     * @param args              arguments which will passed to each {@link #newChild(Executor, Object...)} call
     */
    protected MultithreadEventExecutorGroup(int nThreads, ThreadFactory threadFactory, Object... args) {
        this(nThreads, threadFactory == null ? null : new ThreadPerTaskExecutor(threadFactory), args);
    }

    /**
     * Create a new instance.
     *
     * @param nThreads          the number of threads that will be used by this instance.
     * @param executor          the Executor to use, or {@code null} if the default should be used.
     * @param args              arguments which will passed to each {@link #newChild(Executor, Object...)} call
     */
    protected MultithreadEventExecutorGroup(int nThreads, Executor executor, Object... args) {
        this(nThreads, executor, DefaultEventExecutorChooserFactory.INSTANCE, args);
    }

    /**
     * Create a new instance.
     *
     * @param nThreads          the number of threads that will be used by this instance.
     * @param executor          the Executor to use, or {@code null} if the default should be used.
     * @param chooserFactory    the {@link EventExecutorChooserFactory} to use.
     * @param args              arguments which will passed to each {@link #newChild(Executor, Object...)} call
     */
    protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
                                            EventExecutorChooserFactory chooserFactory, Object... args) {
        if (nThreads <= 0) {
            throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));
        }

        //任务执行器，每个task创建一个新的线程执行
        if (executor == null) {
            executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
        }

        //创建EventExecutor数组，长度nThreads
        children = new EventExecutor[nThreads];

        for (int i = 0; i < nThreads; i ++) {
            boolean success = false;
            try {
                //循环调用子类实现
                children[i] = newChild(executor, args);
                success = true;
            } catch (Exception e) {
                // TODO: Think about if this is a good exception type
                throw new IllegalStateException("failed to create a child event loop", e);
            } finally {
                if (!success) {
                    //如果失败，循环所有EventExecutor进行关闭
                    for (int j = 0; j < i; j ++) {
                        children[j].shutdownGracefully();
                    }

                    for (int j = 0; j < i; j ++) {
                        EventExecutor e = children[j];
                        try {
                            while (!e.isTerminated()) {
                                e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
                            }
                        } catch (InterruptedException interrupted) {
                            // Let the caller handle the interruption.
                            Thread.currentThread().interrupt();
                            break;
                        }
                    }
                }
            }
        }

        //创建一个选择器，children是一个数组，里面每个元素就是一个EventLoop
        chooser = chooserFactory.newChooser(children);

        final FutureListener